This application describes a 4-year training program for an academic career in pediatrics. The Principal Investigator (Principal Investigator) has completed residency training in pediatrics at Children's Hospital of Michigan/Wayne State University School of Medicine and fellowship training in both pediatric emergency medicine and medical toxicology at Children's Hospital of Boston/Harvard Medical School. He will now expand upon his scientific skills through a unique inter-departmental collaboration between the Department of Neurosciences and the Departments of Environmental Health Sciences and Pediatrics, the Principal Investigator's primary and secondary departments, respectively, at Case Western Reserve University (CWRU). The inter-departmental collaboration will provide the Principal Investigator with mentored research, career development, and training activities for a future career as an independent investigator. This program will promote the command of the regulatory programs that govern the development of the vertebrate serotonin (5-HT) system, and its condition after perturbation with antenatal Selective Serotonin Reuptake Inhibitor (SSRI) exposure. Dr. Evan Deneris will mentor the Principal Investigator's scientific development and is a recognized leader in the field of molecular genetics of the brain 5-HT neurotransmitter system. He has made fundamental contributions to the understanding of the genetic mechanisms that act across the lifespan to regulate 5-HT system function and how these mechanisms impact 5-HT modulated behaviors. His studies have identified the Pet-1 transcription factor that functions in an embryonic regulatory network to specify 5-HT neurons in the mouse ventral hindbrain. Dr. Deneris is a Professor in the Department of Neurosciences and has trained numerous graduate students and postdoctoral fellows. Also, an Advisory Committee of highly-regarded CWRU investigators will provide scientific and career guidance. Using BAC transgenic tools that were made possible by the identification of the Pet-1 cis regulatory region that directs highly reproducible expression of transgenes in developing and adult brain 5-HT neurons, Dr. Deneris developed the ePet-EYFP transgenic mouse line whose 5-HT neurons are genetically marked with enhanced yellow fluorescent protein (EYFP) throughout the lifespan. These mice allow for unprecedented access to 5-HT neurons and targeted gene expression studies specifically in 5HT neurons at any stage of life. The proposed experiments will entail antenatal exposure of pregnant ePet-EYFP mice with the SSRI, fluoxetine. Subsequently, phenotypes of offspring will be examined using behavioral assays and molecular techniques. The specific aims include: 1) Establishing the ePet-EYFP mouse as a valid model of behavioral pathogenesis resulting from antenatal SSRI exposure, and 2) Investigating the molecular effects of antenatal SSRI exposure in ePet-EYFP mice. The combined behavioral and molecular approach in ePet-EYFP mice is unique in basic mental health research. Together, they will test the Principal Investigator's hypothesis that antenatal SSRI exposure will lead to behavioral pathogenesis from perturbations in the regulatory programs that govern 5-HT neuron development.